Smac mimetic-derived augmentation of chemotherapeutic response in experimental pancreatic cancer

Niranjan Awasthi,Jason E Toombs,Rolf A Brekken,Roderich E Schwarz,Margaret A Schwarz,Amanda Kirane

doi:10.1186/1471-2407-11-15

Niranjan Awasthi, Jason E Toombs + Show 4 more

Open Access

https://doi.org/10.1186/1471-2407-11-15

Copy DOI

Abstract

BackgroundPancreatic ductal adenocarcinoma (PDAC) is highly resistant to conventional chemotherapy, in part due to the overexpression of inhibitors of apoptosis proteins (IAPs). Smac is an endogenous IAP-antagonist, which renders synthetic Smac mimetics attractive anticancer agents. We evaluated the benefits of combining a Smac mimetic, JP1201 (JP), with conventional chemotherapy agents used for PDAC management.MethodsCell viability assays and protein expression analysis were performed using WST-1 reagent and Western blotting, respectively. Apoptosis was detected by annexin V/propidium iodide staining. In vivo tumor growth and survival studies were performed in murine PDAC xenografts.ResultsJP and gemcitabine (Gem) inhibited PDAC cell proliferation with additive effects in combination. The percentage of early apoptotic cells in controls, JP, Gem and JP + Gem was 17%, 26%, 26% and 38%, respectively. JP-induced apoptosis was accompanied by PARP-1 cleavage. Similar additive anti-proliferative effects were seen for combinations of JP with doxorubicin (Dox) and docetaxel (DT). The JP + Gem combination caused a 30% decrease in tumor size in vivo compared to controls. Median animal survival was improved significantly in mice treated with JP + Gem (38 d) compared to controls (22 d), JP (28 d) or Gem (32 d) (p = 0.01). Animal survival was also improved with JP + DT treatment (32 d) compared to controls (16 d), JP (21 d) or DT alone (27 d).ConclusionsThese results warrant further exploration of strategies that promote chemotherapy-induced apoptosis of tumors and highlight the potential of Smac mimetics in clinical PDAC therapy.

Highlights

Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to conventional chemotherapy, in part due to the overexpression of inhibitors of apoptosis proteins (IAPs)
Effect of JP and Gem on PDAC cell proliferation In vitro WST-1 assay was performed to examine the effect of JP and Gem on PDAC cell proliferation
Effect of JP and Gem on PDAC apoptosis We examined if the inhibition in AsPC-1 cell viability by JP and Gem could in part be due to induction of apoptosis

Summary

Introduction

Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to conventional chemotherapy, in part due to the overexpression of inhibitors of apoptosis proteins (IAPs). We evaluated the benefits of combining a Smac mimetic, JP1201 (JP), with conventional chemotherapy agents used for PDAC management. Many cancer cells possess apoptotic dysfunction that correlates with tumor aggressiveness and resistance to conventional chemotherapy [13]. Various antiapoptotic proteins including inhibitors of apoptosis (IAPs) have been linked to cancer cell escape from apoptosis [14,15]. Smac inhibits IAPs and promotes caspase activation and apoptosis [19,20]. Small-molecule mimetics of Smac have been developed that can promote cancer cell apoptosis either alone or in combination with other proapoptotic agents [16,21,22]. The Smac mimetic JP1201 (JP) has recently been shown to augment the Gem response in PDAC MIA PaCa-2 cells [23]

Methods

Results

Discussion

Conclusion